Car-Parrinello Molecular Dynamics Calculations Research Articles

Water Splits To Degrade Two-Dimensional Group-IV Monochalcogenides in Nanoseconds.

The experimental exfoliation of layered group-IV monochalcogenides—semiconductors isostructural to black phosphorus—using processes similar to those followed in the production of graphene or phosphorene has turned out unsuccessful thus far, as if the chemical degradation observed in black phosphorus was aggravated in these monochalcogenides. Here, we document a facile dissociation of water by these materials within 10 ns from room-temperature Car–Parrinello molecular dynamics calculations under standard temperature and pressure conditions. These results suggest that humidity must be fully eradicated to exfoliate monolayers successfully, for instance, by placing samples in a hydrophobic solution during mechanical exfoliation. From another materials perspective, these two-dimensional materials that create individual hydrogen ions out of water without illumination may become relevant for applications in hydrogen production and storage.

Revealing a Discontinuity in the Degradation Behavior of CH3NH3PbI3 during Thermal Operation

The advance of innovative photovoltaics based on hybrid perovskites is currently forced to face their stability and durability through the rationalization of the phenomena occurring into the lattice under conditions which mimic the material operation. In this framework, we study the structural modifications of MAPbI3 layers by in situ structural and optical analyses upon recursive thermal cycles from 30 to 80 °C in different annealing environments. We reveal an acceleration of the material modification, above what expected, as the threshold of the tetragonal to cubic transition (∼50 °C) is surpassed. This produces discontinuities in the degradation rate, bandgap value, and dielectric behavior of the MAPbI3 layer. The phenomenon is put in relationship with the order–disorder lattice modifications described by Car–Parrinello molecular dynamics calculations and reveals that the action of species from humid air becomes largely more effective above 50 °C for reasons related to the increased accessibility/react...

Analysis of librational modes of ice XI studied by Car–Parrinello molecular dynamics

Theoretical infrared spectra of ice XI at 4 and 40K were obtained by Car–Parrinello molecular dynamics calculations and evaluating the dipole moment using maximally-localized Wannier functions. In order to improve the agreement between theoretical and experimental spectra, the Kramers–Kronig relations were applied. Based on analysis of power and polarization spectra the assignment of modes was carried out. The results were compared with experimental and theoretical spectra of ice XI, performed by other authors. Such simulations can be very useful while investigating the existence of ice XI in space.

On the Structures and Growing Mechanisms of the Ti@C2n (2n = 26 - 50) Endohedral Fullerenes

During the last years, several mechanisms have been suggested in relation to the formation of fullerenes. One of them involves the ingestion of a C2 unit by an already formed fullerene. In this communication, we summarize the theoretical investigations carried out for the series of Ti@C2n endohedral fullerenes, with 2n = 26 to 50. After a thorough exploration of the most favorable isomers, potential energy surfaces associated with the C2 addition, and the topology of the involved structures we have concluded that in contrast to large endohedral metallofullerenes (2n>60) in which the empty cage is different to the optimal cage that hosts a metal ion or a small cluster, in small endohedral fullerenes encapsulating a tetravalent ion the empty and hosting cage often coincides. The addition of a C2 unit to an already formed Ti@C2n fullerene is always an exergonic reaction. Most of the lowest in energy isomers are formally linked by a C2 addition and a Stone-Wales transformation. Car-Parrinello Molecular Dynamics calculations show that after the attack of a C2 unit to one of the C atoms of the Ti@C2n system, the formation of the second C-C bond that closes the cage is an improbable event and must be accelerated using Metadynamics or via an external collision, for example with He atoms that are present in the sample.

Comparison of Resonance Assisted and Charge Assisted Effects in Strengthening of Hydrogen Bonds in Dipyrrins

This paper deals with the study of two types of hydrogen bonding: a quasi-aromatic hydrogen bonding in dipyrromethene and the ionic one in dipyrromethane. The study focuses on two phenomena-the proton transfer process and tautomeric equilibrium. Metric parameters and spectroscopic assignments have been calculated; this allowed a further comparison of spectral features calculated with four methods (Car-Parrinello molecular dynamics (CPMD), ab initio, density functional theory (DFT), and numerical calculation of anharmonic vibrational levels via a solution of the corresponding 1D Schrödinger equation). A significant dynamics of the bridged proton and bent vibration of pyrrole fragments in dipyrromethane have been exposed by the CPMD calculations. The prevailing of the ionic effect over the π-electronic coupling in the strengthening of the hydrogen bonding has been shown on the basis of the calculated structural, electron-topological, and spectral data as well as potential energy surface (PES). The analysis of the aromaticity and electronic state of pyrrole and chelate moieties depending on the tautomeric equilibrium by the quantum theory of atoms in molecules (QTAIM) method was conducted. The principle divergence in the behavior of aromaticity of the chelate chains in the analyzed compounds was demonstrated.

Structural phase transitions induced by pressure in ammonium borohydride

A combined experimental and theoretical study of hydrogen-rich ammonium borohydride (NH4BH4) subjected to pressures up to 10 GPa indicates two phase transitions, detected by synchrotron radiation powder X-ray diffraction, Raman spectroscopy and Car-Parrinello molecular dynamics calculations, at 1.5 and 3.4 GPa. The ambient pressure, face-centred cubic phase of NH4BH4 transforms into a highly disordered intermediate structure which then evolves upon increasing pressure into an orthorhombic, distorted CsCl structure. The structure of the latter phase was solved using ab initio computational techniques and from a Rietveld full pattern refinement of the powder X-ray diffraction data.

Multiscale Quantum Simulation of Resistance Switching in Amorphous Carbon

Ab initio calculations on the basis of quantum molecular dynamics CPMD (Car-Parrinello Molecular Dynamics) code are used to simulate the resistance-change in amorphous carbon. These simulations show that the resistance change is related to changes in the atomic structures of conducting dots due to thermal effects. Different scenarios of the temperature growth and possible annealing procedures are considered. The energy gap between two structural stages and the density of states at different temperatures are determined. The electronic density is used to identify conductive pathways through the system. A multiscale model of resistance switching based on the reduced Ehrenfest molecular dynamics is suggested. This computational model combines long-time-scale CPMD calculations of thermodynamic equilibrium states with the short-time-scale calculations of transitions to a new configurations using excited states of the electronic system. The simulations were performed on the IBM Blue Gene/P supercomputer at Moscow State University.

Ion-orbital coupling in Car-Parrinello calculations of hydrogen-bond vibrational dynamics: Case study with the NH3–HCl dimer

We have performed Car-Parrinello molecular dynamics (CPMD) calculations of the hydrogen-bonded NH(3)-HCl dimer. Our main aim is to establish how ionic-orbital coupling in CPMD affects the vibrational dynamics in hydrogen-bonded systems by characterizing the dependence of the calculated vibrational frequencies upon the orbital mass in the adiabatic limit of Car-Parrinello calculations. We use the example of the NH(3)-HCl dimer because of interest in its vibrational spectrum, in particular the magnitude of the frequency shift of the H-Cl stretch due to the anharmonic interactions when the hydrogen bond is formed. We find that an orbital mass of about 100 a.u. or smaller is required in order for the ion-orbital coupling to be linear in orbital mass, and the results for which can be accurately extrapolated to the adiabatic limit of zero orbital mass. We argue that this is general for hydrogen-bonded systems, suggesting that typical orbital mass values used in CPMD are too high to accurately describe vibrational dynamics in hydrogen-bonded systems. Our results also show that the usual application of a scaling factor to the CPMD frequencies to correct for the effects of orbital mass is not valid. For the dynamics of the dimer, we find that the H-Cl stretch and the N-H-Cl bend are significantly coupled, suggesting that it is important to include the latter degree of freedom in quantum dynamical calculations. Results from our calculations with deuterium-substitution show that both these degrees of freedom have significant anharmonic interactions. Our calculated frequency for the H-Cl stretch using the Becke-exchange Lee-Yang-Parr correlation functional compares reasonably well with a previous second-order Møller-Plesset calculation with anharmonic corrections, although it is low compared to the experimental value for the dimer trapped in a neon-matrix.

Car-Parrinello Molecular Dynamics Simulations of Microstructure Properties of Liquid Water, Methanol and Ethanol

采用Car-Parrinello 分子动力学（CPMD）方法分别研究了水、甲醇和乙醇的液体微结构性质.研究结果显示：在水、甲醇和乙醇三个体系中O…O径向分布函数曲线的第一个峰位置分别为0.278、0.276 和0.275nm; O…H径向分布函数曲线的第一个峰位置分别为0.178、0.176和0.177 nm.表明基团（氢原子、甲基、乙基）的差异对O…O第一个峰的位置影响很小.但基团的差异对径向分布函数峰高的影响却很显著,由水到乙醇第一个峰的高度逐渐变高.空间分布函数表明氧原子和氢原子在溶剂分子周围有取向地分布,这与径向分布函数所表现出尖锐的第一个峰相一致.氢键分布分析显示,水、甲醇和乙醇的平均氢键数分别为3.62、1.99 和1.87,表明水形成了网状氢键结构,而甲醇、乙醇形成链状氢键结构.

Enol Tautomers of Watson−Crick Base Pair Models Are Metastable Because of Nuclear Quantum Effects

Intermolecular enol tautomers of Watson-Crick base pairs could emerge spontaneously via interbase double proton transfer. It has been hypothesized that their formation could be facilitated by thermal fluctuations and proton tunneling, and possibly be relevant to DNA damage. Theoretical and computational studies, assuming classical nuclei, have confirmed the dynamic stability of these rare tautomers. However, by accounting for nuclear quantum effects explicitly through Car-Parrinello path integral molecular dynamics calculations, we find the tautomeric enol form to be dynamically metastable, with lifetimes too insignificant to be implicated in DNA damage.

Pressure-driven phase transitions in TiOCl and the family(Ca, Sr, Ba)Fe2As2

Motivated by recent experimental measurements on pressure-driven phasetransitions in Mott insulators as well as the new iron pnictide superconductors, weshow that first principles Car–Parrinello molecular dynamics calculations area powerful method to describe the microscopic origin of such transitions. Wepresent results for (i) the pressure-induced insulator to metal phase transitionin the prototypical Mott insulator TiOCl as well as (ii) the pressure-inducedstructural and magnetic phase transitions in the family of correlated metalsAFe2As2 (A = Ca, Sr, Ba). Comparison of our predictions with existing experimental results yields very goodagreement.

Vibrational frequencies in Car–Parrinello molecular dynamics

Car-Parrinello molecular dynamics (CPMD) are widely used to investigate the dynamical properties of molecular systems. An important issue in such applications is the dependence of dynamical quantities such as molecular vibrational frequencies upon the fictitious orbital mass μ. Although it is known that the correct Born-Oppenheimer dynamics are recovered at zero μ, it is not clear how these dynamical quantities are to be rigorously extracted from CPMD calculations. Our work addresses this issue for vibrational frequencies. We show that when the system is sufficiently close to the ground state the calculated ionic vibrational frequencies are ω(M) = ω(0M)[1 -C(μ/M)] for small μ/M, where ω(0M) is the Born-Oppenheimer ionic frequency, M the ionic mass, and C a constant that depends upon the ion-orbital coupling force constants. Our analysis also provides a quantitative understanding of the orbital oscillation amplitudes, leading to a relationship between the adiabaticity of a system and the ion-orbital coupling constants. In particular, we show that there is a significant systematic dependence of calculated vibrational frequencies upon how close the CPMD trajectory is to the Born-Oppenheimer surface. We verify our analytical results with numerical simulations for N(2), Sn(2), and H/Si(100)-(2×1).

Fermi resonance and strong anharmonic effects in the absorption spectra of the ν-OH ( ν-OD) vibration of solid H- and D-benzoic acid

The vibrational spectra of polycrystalline benzoic acid (BA) and its deuterated derivative were studied over the wide frequency region 4000–10 cm −1 by IR and Raman methods. A theoretical analysis of the hydrogen bond frequency region and calculations at the B3LYP/6-311++G(2d, 2p) level for the benzoic acid cyclic dimer in the gas phase were made. In order to study the dynamics of proton transfer two formalisms were applied: Car–Parrinello Molecular Dynamics (CPMD) and Path Integrals Molecular Dynamics (PIMD). It was shown that the experimentally observed very broad ν-OH band absorption is the result of complex anharmonic interaction: Fermi resonance between the OH-stretching and bending vibrations and strong interaction of the ν-OH stretching with the low frequency phonons. The theoretical analysis in the framework of such an approach gave a good correlation with experiment. From the CPMD calculations it was confirmed that the O–H⋯O bridge is not rigid, with the O⋯O distance being described by a large amplitude motion. For the benzoic acid dimer we observed stepwise (asynchronous) proton transfer.

Toward a comprehensive understanding of solid-state core-level XPS linewidths: Experimental and theoretical studies on theSi 2pandO 1slinewidths in silicates

High resolution X-ray Photoelectron Spectroscopy (XPS) core-level $\text{Si}\text{ }2p$ and $\text{O}\text{ }1s$ spectra of the nonconductors $\ensuremath{\alpha}{\text{-SiO}}_{2}$ (quartz) at 120 and 300 K and vitreous ${\text{SiO}}_{2}$ at 300 K were obtained with a Kratos Axis Ultra XPS instrument (instrumental resolution of $l0.4\text{ }\text{eV}$) which incorporates a unique charge compensation system that minimizes differential charge broadening on nonconductors. The $\text{Si}\text{ }2p$ and $\text{O}\text{ }1s$ linewidths at 300 K ($\ensuremath{\sim}1.1$ and $\ensuremath{\sim}1.2\text{ }\text{eV}$, respectively) are similar for all silicates (and similar to previous thin film ${\text{SiO}}_{2}$ spectra obtained previously), showing that differential charging does not contribute significantly to our spectra. At 120 K, there is a small decrease (0.04 eV) in the $\text{Si}\text{ }2p$ linewidth of $\ensuremath{\alpha}{\text{-SiO}}_{2}$, but no measurable decrease in $\text{O}\text{ }1s$ linewidth. The $\text{O}\text{ }1s$ lines are generally and distinctly asymmetric. We consider all possible sources of line broadening and show that final state vibrational broadening (FSVB) and phonon broadening are the major causes of the broad and asymmetric lines. Previous high resolution gas phase XPS studies have identified large FSVB contributions to the $\text{Si}\text{ }2p$ spectra of ${\text{SiCl}}_{4}$, ${\text{SiF}}_{4}$, and $\text{Si}{({\text{OCH}}_{3})}_{4}$ molecules, and this vibrational structure leads total $\text{Si}\text{ }2{p}_{3/2}$ linewidths of up to $\ensuremath{\sim}0.5\text{ }\text{eV}$, even with individual peak linewidths of $l0.1\text{ }\text{eV}$. The Si atom of $\text{Si}{({\text{OCH}}_{3})}_{4}$ is an excellent analog for Si in crystalline ${\text{SiO}}_{2}$ because the Si-O bond lengths and symmetric stretch frequencies are similar in both compounds. Similar vibrational contributions to the $\text{Si}\text{ }2p$ and $\text{O}\text{ }1s$ spectra of solid silicates are anticipated if the $\text{Si}\text{ }2p$ and $\text{O}\text{ }1s$ core-hole states produce similar changes to the Si-O bond length in both phases. To investigate the possibility, Car-Parrinello molecular dynamics calculations were performed and show that changes to Si-O bond lengths between ion and ground states $(\ensuremath{\Delta}r)$ for both $\text{Si}\text{ }2p$ and $\text{O}\text{ }1s$ hole states are similar for both crystalline ${\text{SiO}}_{2}$ and gaseous $\text{Si}{({\text{OCH}}_{3})}_{4}$. $\ensuremath{\Delta}r$ are $\ensuremath{-}0.04\text{ }\text{\AA{}}$ for $\text{Si}\text{ }2p$ and $\ensuremath{\sim}+0.05\text{ }\text{\AA{}}$ for $\text{O}\text{ }1s$ in both compounds. Indeed, the vibrational envelope from the $\text{Si}\text{ }2p$ spectrum of $\text{Si}{({\text{OCH}}_{3})}_{4}$, broadened to our instrumental linewidth of 0.4 eV, accounts for the majority $(\ensuremath{\sim}0.8\text{ }\text{eV})$ of the $\text{Si}\text{ }2{p}_{3/2}$ linewidth for crystalline ${\text{SiO}}_{2}$ $(\ensuremath{\sim}1.1\text{ }\text{eV})$ with phonon broadening accounting for the remainder. The results provide excellent support for the tenet that final state vibrational splitting, as seen in the gas phase molecules, similarly affects the solid-state spectra. The calculations also indicate that the $\text{O}\text{ }1s$ linewidths should be larger than the $\text{Si}\text{ }2p$ linewidths, as observed in our spectra. FSVB should also lead to small peak asymmetries, as seen in the $\text{O}\text{ }1s$ spectra. The contribution of phonon broadening to the linewidth is also evaluated and shown to be comparable to the FSVB contribution at 120 and 300 K but considerably smaller at very low temperatures.

Solvent Dependence on Bond Length Alternation and Charge Distribution in Phenol Blue: A Car−Parrinello Molecular Dynamics Investigation

Car-Parrinello mixed quantum mechanics/classical mechanics (CP-QM/MM) calculations are performed for phenol blue (PB) in chloroform and water solvents along with Car-Parrinello molecular dynamics (CPMD) calculations on PB in the gas phase. The solvent effect on molecular geometry, particularly of bond length alternation (BLA), has been studied. As reported for similar donor-acceptor polyenic systems, a remarkable solvent effect is seen on the BLA. The calculated BLA parameter suggests that PB is in the neutral form in the gas phase and in chloroform solvent, while in water, it is cyanine-like, which is a mixture of neutral and zwitterionic resonant forms, something that clarifies the controversial reports on the structure of PB in chloroform. We have also verified that the structures obtained from CPMD and CP-QM/MM calculations are correct by calculating absorption spectra for PB in the gas phase and in chloroform solvent and compared with experimental results. To understand the structure for PB in the gas phase and in water solvent, we have carried out Mayer bond order analysis, supporting that the structure of PB in water is cyanine-like. Moreover, PB in water is found to be much more polarized than that in chloroform solvent. Overall, the present work demonstrates that CP-QM/MM calculations can be used to understand the solvent effects on polyenic and merocyanine-like systems, which are usually difficult to model.

1,2-Dichloroethane in Haloalkane Dehalogenase Protein and in Water Solvent: A Case Study of the Confinement Effect on Structural and Dynamical Properties

The structural and dynamical properties of an individual molecule is much affected by changes in a surrounding solvent or protein environment. The focus of the present study is to investigate such changes between proteins and solvents, using as an illustrating example the structure and dynamics of 1,2-dichloroethane (DCE) within haloalkane dehalogenase (HAD) as protein and within water as solvent. We have studied DCE within HAD using Car-Parrinello molecular dynamics calculations in a quantum mechanics/molecular mechanics set-up. We find that the C-Cl bond length is shorter in HAD when compared to solution phase value, whereas the net atomic charges and dipole moment are significantly larger than the solution phase values. In contradiction to the usual trend that molecules in the vicinity of the proteins are less polar, we report the observation that the protein environment indeed polarizes the DCE solute more than the water solvent. Furthermore, within the protein environment we do not observe any conformational transition between gauche and trans conformers, and the DCE remains in the more polar gauche conformer during the entire simulation time scale. However, the trans conformer interconverts to the gauche conformer spontaneously within 0.4 ps, which clearly indicates that the trans conformer is unstable within the HAD protein. In contrast, the scatter diagram of total Kohn-Sham energy and dihedral angle between Cl-C-C-Cl atoms shows that the gauche and trans conformers have comparable energies in water. Overall, the present calculations show the within the protein not only the structure of DCE is altered but also that the conformational interconversion dynamics is affected very much. To investigate the confinement effect on the conformational equilibrium, we have also carried out force-field molecular dynamics calculations which show that the population of trans conformer is significantly lower within the protein when compared to that in water solvent.

Solvent Dependence of Conformational Distribution, Molecular Geometry, and Electronic Structure in Adenosine

Solvation dynamics of adenosine in water and chloroform solvents under ambient conditions has been investigated using both force-field molecular dynamics (MD) and first-principles Car-Parrinello molecular dynamics (CPMD) calculations. First, the solvent dependence of the equilibria between anti-syn forms, C((3'))-endo-C((2'))-endo conformations, and carbinol group rotamers has been discussed from MD calculations. We find that in both the solvents the adenosine molecule can remain either in anti or syn conformations. But, the anti-syn interconversion occurs relatively faster in water solvent than in chloroform solvent. Because of the relatively larger time scale for the interconversion, anti and syn conformational states of adenosine are studied separately in water and chloroform solvents using CPMD calculations. The dipole moments calculated from CPMD and MD calculations for adenosine in water are significantly larger than in chloroform solvent. On the basis of the CPMD calculations, the syn form of adenosine in water has a larger dipole moment than the anti form. Moreover, the molecular geometry of anti and syn forms of adenosine in these two solvents is reported. We report a remarkable solvent effect on the geometry of the anti form of the adenosine, which is attributed to differences in the intermolecular and intramolecular hydrogen-bonding stabilization. We also report the solvent effect on the frontier Kohn-Sham orbitals and energy gaps for anti-syn conformational states. Finally, we report the solvation shell structure of adenosine in both the solvents, and we find that the solvent-solute interaction is site-specific in the case of water while in chloroform solvent the interaction is globular isotropic in nature.

Car−Parrinello MD Simulations for the Na+−Phenylalanine Complex in Aqueous Solution

Car-Parrinello molecular dynamics (CPMD) calculations are presented for a Na (+)(Phe) complex in aqueous solution and for various stable Na (+)(Phe) complexes and Na (+)(H 2O) n clusters in the gas phase (with up to six water molecules). The CPMD results are compared to available experimental and ab initio reference data, to DFT results obtained with various combinations of density functionals and basis sets, and to previous classical mechanics MD simulations. The agreement with the reference data in the gas phase validates the CPMD method, showing that it is a valid approach for studying these systems and that it describes correctly the competing Na (+)-Phe and Na (+)-H 2O interactions. Analysis of MD trajectories reveals that the Na (+)(Phe) complex in aqueous solution maintains a stable configuration in which the Na (+) cation hovers above the phenyl ring, at an average distance of 3.85 A from the ring center, while remaining strongly bound to one of the carboxylic oxygens of Phe. Constrained MD simulations indicate that the free energy barrier opposing dissociation of the complex exceeds 5.5 kcal/mol. We thus confirm that "cation- pi" interactions between alcali cations and the pi ring, combined with other kinds of interactions, may allow aromatic amino acids to overcome the competition with water in binding a cation.

Investigations into conformational transitions and solvation structure of a 7-piperidino-5,9-methanobenzo[8] annulene in water

Solvation shell structure of a 7-piperidino-5,9-methanobenzo[8] annulene (PMA) in water has been investigated in ambient conditions using both molecular dynamics (MD) and Car-Parrinello molecular dynamics (CPMD) calculations. From the MD calculations, we find that this molecule exists in three major conformational states out of which two are in twist-boat forms and one in chair form. Due to the limited time scale accessible in CPMD simulations, we have studied all the three conformational states separately using CPMD. The molecular geometry, electronic charge distribution and solvation structure for all three forms are investigated. The stability order of the chair and twist-boat conformations in water solvent has been reversed when compared to the gaseous phase results and in the case of polar aprotic solvents (J. Org. Chem., 1999, 61, 5979). From the radial distribution function, we find that the solvent density around the chair form is significantly lower, which has to be directly related to the smaller solvent accessible area for this conformation and this is in complete agreement with earlier reports. Among the findings are that the solvation shell structure around the nitrogen atom in the chair form of PMA is considerably different from the open conformational forms or the twist-boat forms. The dipole moment for the closed form is found to be significantly larger when compared to the twist-boat forms.

A combined spectroscopic and theoretical approach to investigate structural properties of Co(ii)/Co(iii) tris-cysteinato complexes in aqueous medium

Physiological and toxicological effects of metallic ions depend on their speciation and on the structure of their associated bioligand complexes. In the field of chemical and/or nuclear toxicological studies, we are investigating cobalt complexes with biorelevant ligands such as amino acids or peptides. The aqueous reaction of cobalt dichloride with an excess of cysteine (Cys, C3H5NSO22−) in a basic medium under an anaerobic atmosphere and subsequent oxidation by O2, afforded the mononuclear complexes Co(II):3Cys and Co(III):3Cys, respectively. A combination of X-ray absorption spectroscopy (XAS) measurements and Car-Parrinello molecular dynamics (CPMD) simulations allowed us to assess structural features of the already explored Co(III):3Cys complex. Inclusion of the temperature effects in the CPMD calculations gives an implicit access to disorder effects in the extended X-ray absorption fine structure (EXAFS) equation. The very good agreement between the measured and the simulated data showed the accuracy of these models provided by CPMD. The present investigation is completed by new UV-visible, X-ray absorption near edge structure (XANES) and electron paramagnetic resonance (EPR) data of Co(II):3Cys. These data are consistent with a Co(II) high-spin d7 complex in a distorted octahedral geometry. This work contributes to the knowledge of topics such as metal–bioligand interaction which is of major interest in the field of bioinorganic chemistry.